Ground-mapping radar involves user management of the tilt of the antenna to optimize the area of the ground illuminated by the radar beam. To reduce operator workload, automatic means of adjusting the tilt have been developed that utilize the aircraft's altitude and the range selection of the radar. This calculation assumes a flat earth referenced to aircraft altitude above terrain but does not consider the differences between the terrain below the aircraft and the terrain being mapped. Thus, over widely varying terrain, the radar beam is not optimally illuminating the desired surface.